Can trees talk to each other with fungal networks? Study raises doubts

Akin to the Ents from "The Lord of the Rings," there is an idea in modern botany that trees can "talk" to one another through a delicate web of fungus filaments that grows underground. The idea is so alluring that it has gained traction in popular culture and has even been termed the "wood-wide network."

However, according to Justine Karst, associate professor from the University of Alberta's Faculty of Agricultural, Life, and Environmental Sciences, it could all be nonsense. In a new study, Karst and two colleagues challenge three commonly held beliefs about the abilities of underground fungi called "common mycorrhizal networks" (CMNs) that connect the roots of different plants.

“It’s great that CMN research has sparked interest in forest fungi, but it’s important for the public to understand that many popular ideas are ahead of the science,” says Karst.

Science has shown that CMNs exist, but the researchers say there is not enough evidence to show that these networks are suitable for trees and their seedlings. Karst and co-authors Melanie Jones of the University of British Columbia Okanagan and Jason Hoeksema of the University of Mississippi looked at data from previous field studies to see if the widely held beliefs were true.

For example, one of the claims that CMNs are common in forests was not backed up by enough scientific evidence. Another claim that older trees use CMNs to give seedlings resources like nutrients and that this helps them survive and grow was also not evident from previous studies.

A review of 26 studies found that while trees can move resources underground, CMNs only sometimes facilitate that flow, and seedlings often don't benefit from CMN access. Overall, their analysis showed that there was almost as much evidence that connecting to a CMN would help or hurt seedlings as there was that it would have no effect.

Karst and her co-authors say that there isn't a single field study that has been peer-reviewed and published that backs up the third claim, which is that adult trees prefer to send resources or "warning signs" of insect damage to young trees through CMNs.

Researchers say that exaggerated information can change and distort how people talk about CMNs, which could affect how forests are managed.

“Distorting science on CMNs in forests is a problem because sound science is critical for deciding how forests are managed. It’s premature to base forest practices and policies on CMNs per se without further evidence. And failing to identify misinformation can erode public trust in science,” Karst explained.

You can review the study in the Nature Ecology and Evolution journal.